1. Technical Field
The present invention relates to the touch detecting field, and more particularly to a touch detecting method applied to a flat display device with an in-cell touch panel and a flat display device with an in-cell touch panel.
2. Description of the Related Art
With the rapid development of science and technology, since flat display device (such as, liquid crystal display device) has many advantages such as high image quality, little size, light weight and wide application-range, etc., it is widely applied to various consumer electronics products, such as mobile phones, notebook computers, desktop display devices and televisions, etc., and has gradually substituted conventional cathode ray tube (CRT) display to be a main trend of the display devices.
Touch device provides a new human-machine interface, and it is more intuitional in use and more suitable for the human nature. If the touch device is integrated with the liquid crystal display device together, the liquid crystal display device can have touch function, and it is a development trend of the liquid crystal display devices.
Refer to FIG. 1, which is a schematic structure view of a flat display device with in-cell touch panel. As shown in FIG. 1, the flat display device 10 comprises a plurality of gate lines G1˜G4, . . . , Gn+1˜Gn+4, . . . (n=0, 4, 8, . . . ), a plurality of data lines 11, a plurality of pixel transistors 12, a plurality of pixel electrodes 13, a plurality of sense units 14 and a plurality of readout lines 15. The gate lines G1˜G4, . . . , Gn+1˜Gn+4, . . . are arranged crossing over with the data lines 11, and thereby dividing the flat display device 10 into a plurality of pixel regions (not marked). Each of the pixel regions has a pixel transistor 12 and a pixel electrode 13 disposed therein, and the pixel transistor 12 in each of the pixel regions is electrically coupled to a corresponding one of the gate lines and a corresponding one of the data lines. Thus a gate signal provided on the corresponding gate line is configured for determining whether switching on the pixel transistor 12, and a data signal provided on the corresponding data line is transmitted to the pixel electrode 13 when the pixel transistor 12 is switched on. This technology is well-known for the persons skilled in the art, and thus will not be described in detail herein.
The sense units 14 are disposed in some of the pixel regions of the flat display device 10 respectively. Furthermore, each of the sense units 14 is electrically coupled to a corresponding one of the gate lines (such as the gate line Gn+3 as shown in FIG. 1, wherein n=0, 4, 8 . . . ) and a corresponding one of the readout lines 15, thus the gate signal provided on the corresponding gate line drives this sense unit 14, and this sense unit 14 further is electrically coupled to a readout unit 20 as shown in FIG. 2 through the corresponding readout line 15. In the flat display device 10 as shown in FIG. 1, each of the sense units 14 is configured for sensing 4×4 pixel regions (as denoted by the solid rectangle on the left-top corner of FIG. 1).
Refer to FIG. 2, which is a schematic circuit block diagram of a readout unit. As shown in FIG. 2, the readout unit 20 comprises an operational amplifier 21, a first capacitor 22, a first switch 23, a second switch 24, a second capacitor 25, a third switch 26, a third capacitor 27 and a processor 28. A positive input terminal of the operational amplifier 21 is electrically coupled to a reference voltage Vref, and a negative input terminal thereof is electrically coupled to the readout line 15 to receive the readout signal in the readout line 15. The first capacitor 22 is electrically between the negative input terminal and an output terminal of the operational amplifier 21, and the first switch 23 is electrically coupled with the first capacitor 22 in parallel. The second switch 24 and the third switch 26 are electrically coupled between the output terminal of the operational amplifier 21 and the processor 28 in parallel. The second capacitor 25 is electrically coupled between the second switch 24 and a grounding potential, and the third capacitor 26 is electrically coupled between the third switch 26 and the grounding potential. The processor 28 is electrically coupled to the second capacitor 25 and the third capacitor 26.
Refer to FIG. 3, which is a schematic timing sequence view of various signals of a conventional touch detecting method. As shown in FIGS. 1-3, a sample signal MUX_T_HS is enabled in a period between driving the corresponding gate line Gn+3 and the nearest gate line Gn+2 preceding the gate line Gn+3 of each of the sense units 14, thus the second switch 24 controlled by the sample signal MUX_T_HS is switched on. At this moment, the readout signal in the readout line 15 passes through the switched-on first switch 23 and the switched-on second switch 24 to be transmitted and stored into the second capacitor 25 as a sample reference signal VHS. Then, a sense readout signal MUX_T_HR is enabled in another period between driving the corresponding gate line Gn+3 of each of the sense unit 14 and the nearest gate line Gn+4 succeeding the gate line Gn+3, thus the third switch 26 controlled by the sense readout signal MUX_T_HR is switched on. At the moment, the first switch 23 is switched off due to the signal MUX_RESET, the readout signal in the readout line 15 passes through the operational amplifier 21 and the switched-on third switch 26 to be transmitted and stored into the third capacitor 27 as a sense signal VHR. Finally, the processor 28 judges whether the sense unit 14 is touched according to the sample reference signal VHS stored in the second capacitor 25 and the sense signal VHR stored in the third capacitor 27.
However, as shown in FIG. 3, when the flat display device 10 displays a pattern, the inputted gate signals would cause a capacitance-coupling phenomenon/effect to the sense unit 14, to influence the readout signal in the readout line 15 such that a capacitance-coupling noise is produced in the readout signal. In detail, when the flat display device 10 displays a normal pattern, every two gate lines reverse the polarity once, thus it generates a slight capacitance-coupling phenomenon to the sense unit 14, the capacitance-coupling noise of the readout signal in the readout line 15 is slight, and it will not influence the sense result. When the flat display device 10 displays a specific pattern, every one gate line reverse the polarity once, thus it generates a large capacitance-coupling phenomenon to the sense unit 14, the capacitance-coupling noise of the readout signal in the readout line is large. Specially, since the conventional touch detecting method enables the sample signal MUX_T_HS in the period between driving the corresponding gate line Gn+3 and the previous gate line Gn+2 of the sense units 14, and at the moment the readout signal in the readout line 15 is regarded as the sample reference signal VHS, the capacitance-coupling noise of the specific pattern in the sample reference signal VHS has the polarity opposite to that of the capacitance-coupling noise of the specific pattern in the sense signal VHR. Thus if employing (VHR−VHS) to judge whether the sense unit 14 is touched, the sense result is influenced by the double of the capacitance-coupling noise of the specific pattern. That is, the sense result of the conventional touch detecting method is seriously influenced by the capacitance-coupling noise, and the final sense result thereof may be altered.